JP6040243B2 - Additives for dye-sensitized solar cells - Google Patents

Description

  The present invention relates to at least one imidazole derivative of formula I or 1- (3,3,4,4,4-pentafluorobutyl) imidazole, 1- (3,3,4,4,4-penta Use of fluorobutyl) 1,2,3-triazole or 1- (2′-thioethyl) ethylimidazole as an additive in dye-sensitized solar cells and at least one compound of formula I or 1- ( 3,3,4,4,4-pentafluorobutyl) imidazole, 1- (3,3,4,4,4-pentafluorobutyl) -1,2,3-triazole or 1- (2′-thioethyl) It relates to a special electrolyte formulation comprising ethylimidazole and a dye-sensitized solar cell.

  Dye-sensitized solar cells using sensitizing dyes have attracted widespread attention. A dye-sensitized solar cell includes, for example, a transparent conductive film formed in this order on a transparent substrate, a porous semiconductor electrode having a sensitizing dye supported therein, a hole transport layer, and a counter electrode including.

Examples of such cells are described in the literature: O'Regan, B. and Graetzel, M. (1991) Nature, 353, 737. The solar cell in this case contains a pair of counter electrodes (anode and cathode) and an electrolyte between them. The electrolyte includes iodide ion pairs having different oxidation states as a hole medium created upon charge separation at the dye-sensitized nanoporous semiconductor-electrolyte interface. The cathode is made of a conductive material, while the anode is a plate of transparent material, such as glass, on which the transparent conductivity of light transmissive tin dioxide (SnO ₂ ) that can be doped with other elements. Made from said plate having a layer as well as a semiconductor titanium dioxide (TiO ₂ ) layer thereon. The TiO ₂ layer is formed of a TiO ₂ semiconductor composed of nanocrystalline particles to which a sensitizing dye is bonded. When the interface between the TiO ₂ nanocrystal layer and the dye is illuminated, electrons are injected into TiO ₂ .

On the other hand, the medium undergoes oxidation in the electrolyte; three iodide ions (I ⁻ ) emit two electrons, resulting in triiodide ions (I ₃ ⁻ ) with a high degree of oxidation. The electrons are then transported through the TiO ₂ nanocrystal layer and collected by the transparent conductive layer while the triiodide ion (I ₃ ⁻ ) diffuses to the cathode and acquires two electrons to acquire iodine. Reduced to fluoride ion (I ⁻ ). In this way, this type of wet cell converts solar energy into electrical energy.

  Dye-sensitized solar cells have been expected to be useful as solar cells for the next generation because of their simple and convenient manufacturing methods and hence reduced material costs.

In order to put the dye-sensitized solar cell into practical use, there is a need for further improvement in conversion efficiency, and therefore the current generated (short circuit current, J _sc ), in the open circuit voltage (V _oc ), and There was a need for an increase in safety and durability.

  The best-functioning dye-sensitized solar cells now contain at least one volatile organic solvent, reducing the viscosity of the electrolyte and thus increasing the ion mobility. The biggest problem here is that, as disclosed in, for example, Yu Bai et al., “High-performance dye-sensitized solar cells based on solvent-free electrolytes produced from eutectic melts”, Nature Materials 2008, 1, For the purpose of being composed solely of ions, the volatility of the electrolyte is removed or reduced by replacing the volatile solvent with an ionic liquid.

One factor limiting the power conversion efficiency of DSSCs based on ionic liquids is the injected electrons or conduction bands in the semiconductor due to a fairly large amount of oxidized sites of the redox couple (eg, I ₃ ⁻ ) in the relevant operating state. It can be a fairly large recombination of electrons (eg TiO ₂ ). In order to increase the open circuit voltage, it is necessary to avoid such recombination, in other words, to suppress leakage current at the semiconductor electrolyte junction.

Leakage currents occur for example in the above reduction of triiodide by conduction band electrons (e ⁻ _cb ), which occurs despite the fact that the TiO ₂ surface is coated with a single layer of dye:
I ₃ ⁻ + 2e ⁻ _cb (TiO ₂ ) → 3I ⁻
Arising from. Triiodide, since relatively a small size, or across the dye layer, or a dye can not be completely coated, that is nanometer surface of the TiO ₂ is exposed to bare a is and redox electrolyte Either have access to a hole of size.

Recombination is typically suppressed by the addition of compounds that are adapted to free sites on the TiO ₂ surface and are therefore thought to prevent access to possible recombination sites for triiodide or free iodine. The Examples of compounds typically used for this purpose are (poly) ether derivatives, amides, esters, nitriles. The current best result is that N-alkyl-benzimidazole (Zhaofu Fei et al., Inorg. Chem. 2006, 45, 10407-10409, A Supercooled Imidazolium Iodide Ion Liquid as a Low-Viscosity Electrolyte for Dye-Sensitized Solar Cells ), 4-tert-butylpyridine (TBP, MK Nazeeruddin et al., J. Am. Chem. Soc. 1993, 115, 6382-6390) or nitrogen-containing complexes such as tetrazole, pyrazole, triazole, pyrazine, pyrimidine, triazine It has been achieved using ring additives (H. Kusama et al., J. Photochem. Photobiol., A Chemistry, 2005, 169-176). TBP and nitrogen-containing heterocyclic additives are believed to be particularly useful in electrolytes comprising at least one volatile organic solvent. The donating properties of nitrogen lone pairs in known heterocyclic additives to date are believed to be responsible for enhanced V _OC .

  Such bases accept protons from either the electrolyte or the sensitized electrode, thus buffering the acidity of the sensitized electrode surface in the finished device, ensuring a stable output over long periods of testing. Alternative or secondary explanations for the effect of doing are believed.

WO 2010/121900 describes the use of N-methylimidazole, N-ethylimidazole and N-propylimidazole as additives for electrolytes in DSSC.
EP 0 986 079 A2 includes —N═C (R ¹ ) — as an additive for the electrolyte in DSSC, where R ¹ is an alkyl group, cycloalkyl group, aralkyl group, aryl group, complex Heterocyclic compounds representing cyclic groups, alkoxy groups, aryloxy groups or acylamino groups are described.

  JP 2005-108664 may be substituted with an alkyl group, an alkynyl group, a phenyl group, an aminophenyl group, a halogenated phenyl group, an amino group, an aminopropyl group, a cyano group, a cyanomethyl group, a halogen group or a benzyl group. Imidazole compounds, especially imidazole, 1- (1-butyl) imidazole, 2-ethyl-4-methylimidazole, 5-ethynyl-1-methylimidazole, 1-phenylimidazole, 4-methyl-2-phenylimidazole, 1- ( 4-aminophenyl) imidazole, 1- (4-fluorophenyl) imidazole, 4-amino-5-cyanoimidazole, 1- (3-aminopropyl) imidazole, 4-cyanomethylimidazole, 4-bromoimidazole, 1-benzyl 2-methylimidazole to aceto An electrolyte solution containing the electrolyte based on the solvent used tolyl describes a dye-sensitized solar cell.

  JP 2006-331995 may be substituted by a hydrocarbon group having 1 to 12 C atoms, in particular an alkyl group having 1 to 6 C atoms and an aryl group having 6 to 12 C atoms A dye-sensitized solar cell is described that includes an electrolyte solution containing an imidazole compound. Electrolytes based on solvents containing 2-ethylimidazole, 4-methylimidazole, 2-propylimidazole in acetonitrile, solid electrolytes containing 2-ethylimidazole and electrolytes containing ethylmethylimidazolium trifluoromethylsulfonylimide and 2-propylimidazole Is described.

  JP 2010-177197 describes additives for DSSC, including phosphonic acids having a long-chain alkyl group of about 13 C atoms, tert-butylpyridine and 1-methoxybenzimidazole.

  However, a novel and improved open circuit voltage can be achieved by shifting the oxide semiconductor conduction band edge in the negative direction and / or by reducing leakage current and thus maximizing the maximum power operating voltage. There is a continuing need for improved additives. The open circuit voltage must be tailored to achieve improved DSC efficiency over a wide temperature range (ie, in the range of 40 ° C. to 120 ° C.), including temperatures above room temperature and well below the temperature at which pigmentation occurs. One important parameter.

The object of the present invention is therefore to induce a shift of the conduction band edge of porous semiconductors, preferably as an additive for dye-sensitized solar cells acting as recombination inhibitors, and / or preferably of TiO ₂ It is to provide alternative and / or improved compounds as agents that induce it.

  Surprisingly, special alkoxyalkylimidazoles or 1- (3,3,4,4,4-pentafluorobutyl) imidazole, 1- (3,3,4,4,4-pentafluorobutyl) -1, 2,3-triazole or 1- (2′-thioethyl) ethylimidazole has been found to meet such requirements.

Without being bound by any theory, the alkoxyalkylimidazoles of formula I induce a shift in the conduction band edge of the porous semiconductor as a recombination inhibitor and / or resulting in an increase in open circuit voltage (V _oc ). It is believed to act as an agent for. Alkoxyalkylimidazole represented by the formula I or 1- (3,3,4,4,4-pentafluorobutyl) imidazole, 1- (3,3,4,4,4-pentafluorobutyl) -1,2 , 3-triazole or 1- (2′-thioethyl) ethylimidazole can thus reduce leakage current, enhance conduction band edge, resulting in both increased V _OC and maximum output voltage V _MAX Acts as an additive.

The present invention therefore firstly provides the formula I
Where
R ^a , R ^b , R ^c , R ^d and R ^e are independently of each other,
H, F, Cl or linear or branched alkyl having 1 to 20 C atoms, optionally partially or fully fluorinated or chlorinated,
n is 1, 2, 3 or 4;
m is 1, 2, 3 or 4.
Is used as an additive in a dye-sensitized solar cell.

  Linear or branched alkyl groups having 1 to 20 C atoms are for example methyl, ethyl, propyl, isopropyl, n-butyl, sec. -Butyl, tert. -Butyl, 1- (2,2-dimethyl) -propyl, pentyl, hexyl, heptyl, octyl, x-methylbutyl in which x is 1; 2 or 3; x-methyl in which x is 1; 2; 3 or 4 Pentyl, x-methylhexyl wherein x is 1; 2; 3; 4 or 5; x-ethylpentyl where x is 1, 2 or 3; x-ethylhexyl where x is 1; 2; 3 or 4; n Nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl and n-eicosyl, which are It can be partially fluorinated, fully fluorinated, partially chlorinated or fully chlorinated.

  The term “fully fluorinated” means that all H atoms are replaced by F atoms in a given alkyl group. The term “partially fluorinated” means that at least one H atom of a given alkyl group is replaced by an F atom. The term “fully chlorinated” means that all H atoms are replaced by Cl atoms in a given alkyl group. The term “partially chlorinated” means that at least one H atom of a given alkyl group is replaced by a Cl atom.

Preferred compounds of the formula I described above are those in which R ^a , R ^b , R ^c , R ^d and R ^e are independently H or F.
R ^a , R ^b , R ^c , R ^d and R ^e are particularly preferably H.
The variable n is preferably 1 or 2.
The variable m is preferably 1 or 2.

  Accordingly, preferred compounds of formula I are 1- (2-ethoxyethyl) imidazole, 1- (2-methoxyethyl) imidazole, 1- (ethoxymethyl) imidazole and 1- (methoxymethyl) imidazole. 1- (2-ethoxyethyl) imidazole is particularly preferred.

At least one compound of the formula I described above or preferably described can be used as a single additive or as a Bronsted or Lewis acidic compound such as the formula Ia
In which R ^a , R ^b , n, R ^c , R ^d , m and R ^e have the meanings defined above and have a monovalent anion, preferably iodide or thiocyanate,
Can be used in combination with its own conjugate acid, which means a compound represented by or various protonated imidazole compounds in the electrolyte.

  Different protonated imidazole compounds are, for example, 1-alkoxyalkylimidazolium iodides or 1-alkylimidazolium iodides. It may also contain other known additives such as (poly) ether derivatives, amides, esters, nitriles or other heterocyclic compounds mentioned as additives in the prior art.

  A compound of formula Ia can be synthesized through reaction with an acid of the compound of formula I, preferably HI or a thiocyanate capable of protonating the compound of formula I. .

  The type of electrolyte useful in a given device, such as a dye-sensitized solar cell, is not limited. The electrolyte may be based on a molecular solvent or organic salt, generally described as a molten salt or ionic liquid. The imidazole of formula I described above or preferably described, or 1- (3,3,4,4,4-pentafluorobutyl) imidazole, 1- (3,3,4,4,4- It is preferred to use pentafluorobutyl) -1,2,3-triazole or 1- (2′-thioethyl) ethylimidazole in electrolytes that do not contain highly volatile molecules, such as low molecular weight organic solvents.

The present invention further relates to at least one compound of the formula I described above or preferably described as redox active species such as iodide / triiodide or Co (II) / Co (III) complex pairs. For example, Co (II) / Co (III) (dbbip) ₂ in which dbbip represents 2,6-bis (1′-butylbenzimidazol-2′-yl) pyridine, and bpy represents bipyridine or an alkylated bipyridine derivative thereof. For the electrolyte formulation comprising Co (II) / Co (III) (bpy) _{3 shown} , the counter anion can be perchlorate, a fluoroperfluoroalkyl phosphate such as perfluoroethyl pentafluorophosphate, or (fluoro ) Cyanoborate, in particular tetracyanoborate, preferably iodide and at least one A redox couple as a redox active species c product salt. This electrolyte composition is used as an electrolyte of a dye-sensitized solar cell.

The electrolyte formulation of the present invention as described above or preferably described, comprising the additive of the present invention as an alternative or improvement to an electrolyte formulation known in the field of electrolyte formulations for dye-sensitized solar cells . When using the additive of the present invention, such electrolyte formulations exhibit comparable or increased power conversion efficiency, avoiding the disadvantages of current known additives, such as tert-butyl-pyridine. The additive of the invention of the formula I described above or preferably described increases the open circuit voltage (V _oc ) and hence the power conversion efficiency of the dye-sensitized solar cell as defined above .

  In chemistry, an electrolyte is any substance that contains free ions that make the substance conductive. The most typical electrolyte is an ionic solution, but molten and solid electrolytes are also possible.

  Therefore, the electrolyte formulation of the present invention is basically a conductive medium because of the presence of at least one substance present in the dissolved or molten state, ie, supports conductivity through the movement of ionic species. However, such conductivity may not be highly relevant to the electrolyte role of dye-sensitized solar cells. Therefore, the scope of the present invention is not limited to highly conductive electrolyte media.

  The term electrolyte can be used for an electrolyte formulation term that fully includes all of the ingredients disclosed for the electrolyte formulation.

  The total concentration of the compounds of formula I described above or preferably described is typically 0.01-30% by weight (% w / w), preferably 0.03-0.0% in the electrolyte formulation. It is in the range of 20% by weight, more preferably 0.1 to 10% by weight.

The electrolyte formulation of the present invention preferably contains iodine (I ₂ ). Particularly preferably it comprises 0.01 to 30% by weight, more preferably 0.05 to 20% by weight and most preferably 0.2 to 10% by weight of I ₂ .

  The electrolyte formulation of the present invention preferably comprises at least one iodide salt.

Iodide salt, I as inorganic or organic cations and anions ^- consists. There is no limitation on the type of cation. However, to limit the amount of different cations in the electrolyte formulation, especially for DSC, organic cations, for example organic compounds containing quaternary nitrogen atoms, preferably cyclic organic cations such as pyridinium, imidazolium, triazolium, pyrrolidinium or morpholinium Organic compounds containing can be used.

Preferably, the electrolyte formulation is a group of organic cations independently.
In which the substituents R ^{2 ′} and R ^{3 ′} each independently represent H or straight-chain or branched alkyl having 1 to 20 C atoms,
R ^{1 ′} and R ^{4 ′} are each independently of each other,
Linear or branched alkyl having 1 to 20 C atoms, which may optionally be partially fluorinated or perfluorinated,
A linear or branched alkenyl having 2 to 20 C atoms and one or more double bonds, which may optionally be partially fluorinated,
A straight-chain or branched alkynyl having 2 to 20 C atoms and one or more triple bonds, which may optionally be partially fluorinated,
Showing,
At least one iodide salt selected from:

  Particularly preferred examples of at least one iodide salt are 1-ethyl-3-methylimidazolium iodide (emim I), 1-propyl-3-methylimidazolium iodide (pmim I), 1-butyl-3 -Methyl-imidazolium iodide (bmim I), 1-hexyl-3-methylimidazolium iodide (hmim I), 1,3-dimethyl-imidazolium iodide (mmim I), 1-allyl-3-methyl It is imidazolium iodide (amim I), N-butyl-N-methyl-pyrrolidinium iodide (bmpl I) or N, N-dimethyl-pyrrolidinium iodide (mmpl I).

  Another component of the electrolyte formulation is one or several additional salts or solvents or additives as further indicated below.

In another embodiment of the invention, the electrolyte formulation comprises an organic cation comprising quaternary nitrogen and halide ions, such as F ⁻ , Cl ⁻ , I ⁻ , polyhalide ions, fluoroalkanesulfonates, fluoro Alkanecarboxylate, tri (fluoroalkylsulfonyl) methide, bis (fluoroalkylsulfonyl) imide, bis (fluorosulfonyl) imide, nitrate, hexafluorophosphate, tris-, bis- and mono- (fluoroalkyl) fluorophosphate, tetracyano Borate, dicyanodifluoroborate, tricyanofluoroborate, tris-, bis- or monoperfluoroalkyl cyanoborate, bis- or monocyano-perfluoroalkyl-mono- or bisfluoroborate Perfluoroalkyl-alkoxy-fluoro-cyanoborate, perfluoroalkyl-alkoxy-dicyanoborate, dicyanamide, tricyanomethide, monohydridotricyanoborate, dihydridodicyanoborate, methyltricyanoborate, ethyltricyanoborate, allyltricia The fluoroalkane contains 1 to 20 C atoms, comprising at least one further salt having an anion selected from noborate, methyl ethyl dicyanoborate, dimethyl dicyanoborate, diethyl dicyanoborate, thiocyanate, alkyl sulfonate or alkyl sulfate. Having, preferably perfluorinated, the fluoroalkyl has 1 to 20 C atoms and the alkyl has 1 to 20 C atoms. The fluoroalkane or fluoroalkyl is preferably perfluorinated.

  Preferably, the further salt is an anion such as thiocyanate, tetracyanoborate, dicyanodifluoroborate, tricyanofluoroborate, monohydridotricyanoborate, dihydridodicyanoborate, methyltricyanoborate, ethyltricyanoborate, allyltricyanoborate. , Methylethyl dicyanoborate, dimethyldicyanoborate, diethyldicyanoborate or a salt comprising a combination thereof.

  In a preferred embodiment of the present invention, the electrolyte formulation of the present invention comprises at least one compound having a tetracyanoborate anion, a dicyanodifluoroborate anion and / or a tricyanofluoroborate anion.

  In a preferred embodiment of the invention, the electrolyte formulation of the invention comprises monohydridotricyanoborate, dihydridodicyanoborate, methyltricyanoborate, ethyltricyanoborate, allyltricyanoborate, methylethyldicyanoborate, dimethyldicyanoborate or Including at least one compound having a diethyldicyanoborate anion.

  Preferably the cation of at least one further salt, or a preferred further salt having one of the anions mentioned above, for example tetracyanoborate, dicyanodifluoroborate anion or tricyanofluoroborate or monohydridotricyanoborate, is preferred Alternatively, it may be selected from among organic cations, preferably a cation containing a quaternary nitrogen atom, particularly preferably a cyclic organic cation such as pyridinium, imidazolium, triazolium, pyrrolidinium or morpholinium.

In another aspect of the invention,
An acid as a proton donor, preferably HI,
Having an inorganic cation and a monovalent anion, preferably having an alkali metal cation or alkaline earth metal cation, iodide, thiocyanate or any other inert anion such as a borate anion such as a tetracyanoborate anion Having salt,
A salt containing a protonated amine, eg, independently of one another, substituted by linear or branched alkyl having 1 to 4 C atoms and not fluorinated having 1 to 8 C atoms May be a partially fluorinated or perfluorinated linear or branched alkoxyalkyl or cycloalkyl having 3 to 7 C atoms, imidazolium, 1-substituted A salt comprising an imidazolium, benzimidazolium or iodide salt or thiocyanate of 1-substituted benzimidazolium,
Alternatively, a guanidinium salt, preferably guanidinium iodide or guanidinium thiocyanate, may be added to the electrolyte formulation comprising at least one additive of the present invention.

  In a preferred embodiment of the invention, an inorganic cation, preferably an alkali metal cation or alkaline earth metal cation, guanidinium cation or a cation which is a protonated amine, preferably imidazolium, benzimidazolium or 1-substituted imidazolium. Or an iodide or thiocyanate having 1-substituted benzimidazolium, wherein the substitution is independently fluorinated having 1 to 4 C atoms and 1 to 8 C atoms. Linear, which may be non-partially fluorinated or partially fluorinated, linear or branched alkoxyalkyl or cycloalkyl having 3 to 7 C atoms Or selected from branched alkyl.

Preferred inorganic salts are lithium iodide, lithium thiocyanate, magnesium iodide or magnesium thiocyanate.
Preferred guanidinium salts are guanidinium iodide or guanidinium thiocyanate.
Preferred salts with cations that are protonated amines are imidazolium iodide, imidazolium thiocyanate, benzimidazolium iodide, benzimidazolium thiocyanate, 1-ethylimidazolium iodide, 1-ethylimidazolium thiocyanate, 1-butyl. Imidazolium iodide or 1-butylimidazolium thiocyanate.

  In one embodiment of the invention, an electrolyte formulation comprising at least one salt having an iodide or thiocyanate anion is preferred, and the cation is a protonated amine.

The following combinations of iodide salts and further compounds and / or additives are preferred:
a) mmim I and emimTCB (1-ethyl-3-methylimidazolium tetracyanoborate)
b) pmim I (1-propyl-3-methylimidazolium iodide) and emim TCB
c) mmim I, amim I and emimTCB
d) mmim I, emim I and emim TCB
e) mmim I, guanidinium iodide and emim TCB

f) mmim I, guanidinium thiocyanate and emim TCB
g) mmim I, lithium iodide and emim TCB
h) mmim I, lithium thiocyanate and emim TCB
i) mmim I, magnesium iodide and emim TCB.
j) mmim I, magnesium thiocyanate and emim TCB.
k) mmim I, imidazolium iodide and emimTCB

l) mmim I, imidazolium thiocyanate and emimTCB
m) mmim I, imidazolium iodide, emim thiocyanate and emimTCB
n) mmim I, benzimidazolium iodide and emimTCB
o) mmim I, benzimidazolium thiocyanate and emimTCB
p) mmim I, 1-ethylimidazolium thiocyanate and emimTCB
q) mmim I, 1-ethylimidazolium iodide and emimTCB

r) mmim I, 1-butylimidazolium iodide and emimTCB
s) mmim I, 1-butylimidazolium thiocyanate and emimTCB
t) mmimI and emim MFB (1-ethyl-3-methylimidazolium fluorotricyanoborate)
u) mmimI and emim DDB (1-ethyl-3-methylimidazolium dicyanodifluoroborate)
v) mmim I and emim MHB (1-ethyl-3-methylimidazolium monohydridotricyanoborate).

emim means 1-ethyl-3-methylimidazolium.
pmim means 1-propyl-3-methylimidazolium.
mmim means 1,3-dimethylimidazolium.
amim means 1-allyl-3-methylimidazolium.

  The electrolyte formulation of the present invention adds, as a further additive, at least one compound containing a nitrogen atom with an unshared electron pair to the compound of formula I of the present invention described above or preferably described above. Or tert. -Butyl-pyridine may also be included. Examples of such compounds are found in EP 0 986 079 A2, starting on page 2, line 40-55, and again extending from page 3, line 14 to page 7, line 54, which is expressly incorporated by reference. Incorporated herein.

The following compounds are also useful as additives in optoelectronic devices, preferably in dye-sensitized solar cells:
1- (2-methoxyethoxymethyl) -1H-imidazole,
1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole,
1- (3,3,4,4,4-pentafluorobutyl) -1,2,4-triazole,
1- (3,3,4,4,4-pentafluorobutyl) -1,2,3-triazole,
N- (3,3,4,4,4-pentafluorobutyl) -benzimidazole,
3-imidazol-1-yl-propylamine,

1- (2′-thioethyl) ethyl-imidazole,
1-n-pentyl-1H-imidazole,
1-n-hexyl-1H-imidazole,
1-n-heptyl-1H-imidazole,
1-n-octyl-1H-imidazole,
1-n-nonyl-1H-imidazole,

1-n-decyl-1H-imidazole,
1-cyclopropyl-1H-imidazole,
1- (cyclopentyl) -1H-imidazole,
1- (cyclohexyl) -1H-imidazole,
1- (cycloheptyl) -1H-imidazole,
1- (cyclooctyl) -1H-imidazole,

1- (1-adamantyl) -1H-imidazole,
1- (2-adamantyl) -1H-imidazole,
1-isopropyl-1H-imidazole,
1- (2-methylpropyl) -1H-imidazole,
1- (3-methylbutyl) -1H-imidazole,
1- (1,1-dimethylethyl) -1H-imidazole,

1- (2-ethylhexyl) -1H-imidazole,
1- (3,7-dimethyloctyl) -1H-imidazole,
1- (2,2,2-trifluoromethyl) ethyl-1H-imidazole 1- (3-propylheptyl) -1H-imidazole,
2-methyl-1H-imidazole,
4,5-dimethyl-1H-imidazole,
4,5-dicyano-1H-imidazole,
2-methyl-4-nitro-1H-imidazole,

4-nitro-1H-imidazole,
1-methyl-2-mercaptoimidazole,
2-phenyl-imidazole,
4-phenyl-imidazole,
1- (trimethylsilylmethyl) -1H-imidazole,
1- (2-cyanoethyl) -1H-imidazole,
1H-imidazole-4,5-dicarboxylic acid,
1- (n-butyl) -4,5-dimethyl-1H-imidazole,

Trans-1,2-cyclohexyl-bis-1 ′, 1 ″ -imidazole 2-methyl-1H-benzimidazole,
2-hydroxy-1H-benzimidazole,
5,6-dimethyl-1H-benzimidazole,
5-nitro-1H-benzimidazole,
1- (4-methoxyphenyl) -1H-imidazole,
1- (4-cyanophenyl) -1H-imidazole,
1- (2,3,4,5,6-pentafluorophenyl) -1H-imidazole,

1- (2-methoxyethyl) benzimidazole,
1- (1-methoxyethoxy) methylbenzimidazole,
1- (2-ethoxyethyl) benzimidazole 1-butyl-1H-benzotriazole,
1- (2-methoxy-ethyl) -1H-benzotriazole,
9-butyl-9H-purine,
1-n-butyl-6-azaindole,
1- (2-methoxyethyl) -6-azaindole,

9- (2-methoxyethyl) -9H-purine,
4,5,6,7-tetrahydro-1H-benzimidazole,
1-butyl-4,5,6,7-tetrahydro-1H-benzimidazole,
4,5,6,7-tetrahydro-1H-benzotriazole,
1-butyl-4,5,6,7-tetrahydro-1H-benzotriazole,

1,2-bis (1-ethoxyimidazole) ethane 1- (2 ′, 2 ′, 6 ′, 6′-tetramethylpiperidino) imidazole 1,4-di- (1-imidazole) butane,
Di- (1-imidazole) methane,
Di- (1-imidazolemethyl) sulfide,

1-methoxyethoxymethylbenzimidazole,
1-methoxyethylindazole,
1-n-butylpyrazole,
1- (2-methoxyethyl) pyrazole.
1- (2-Ethoxyethyl) pyrazole

1- (2-ethoxyethyl) -1,2,3-triazole 1- (2-ethoxyethyl) -1,2,4-triazole,
1-n-butylindazole,
2,2′-biimidazole,
4,4 ′, 5,5′-tetramethyl-2,2′-biimidazole.

  As can be seen in Examples C and D below, additive 1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole and additive 1- (3,3,4,4 , 4-pentafluorobutyl) -1,2,3-triazole provides higher efficiency compared to NBB.

  Accordingly, the present invention provides, in another aspect of the invention, 1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole or 1- (3,3,4,4,4-penta. It relates to the use of fluorobutyl) -1,2,3-triazole as an additive in dye-sensitized solar cells.

  Accordingly, the present invention provides at least 1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole or 1- (3,3,4,4,4-pentafluorobutyl) -1,2 , 3-triazole with redox active species.

As can be shown in Example B, the additive 1- (2′-thioethyl) ethylimidazole provides unexpectedly high efficiency.
Accordingly, the present invention, in another aspect of the present invention, relates to the use of 1- (2′-thioethyl) ethylimidazole as an additive in a dye-sensitized solar cell.
The present invention therefore relates to an electrolyte formulation comprising at least 1- (2′-thioethyl) ethylimidazole together with a redox active species.

  The description for the electrolyte formulation comprising at least one compound of formula I described above or preferably described on page 7 line 15 to page 15 line 5 is also 1- (3,3,4,4 , 4-pentafluorobutyl) imidazole, 1- (3,3,4,4,4-pentafluorobutyl) -1,2,3-triazole or 1- (2′-thioethyl) ethylimidazole Restrain about.

  The electrolyte formulation of the present invention may contain an organic solvent. Preferably, the electrolyte formulation of the present invention comprises less than 50% organic solvent. Particularly preferably, the electrolyte formulation comprises less than 40%, more preferably less than 30%, even more preferably less than 20% and even more preferably less than 10%. Most preferably, the electrolyte formulation contains less than 5% organic solvent. For example, it is substantially free of organic solvents. Percentages are given based on weight percent.

  Organic solvents may be selected from those disclosed in the literature when present in such amounts as indicated above. Preferably, the solvent, if present, is propylene carbonate, ethylene carbonate, butylene carbonate, γ-butyllactone, γ-valerolactone, glutaronitrile, adiponitrile, N-methyloxazolidinone, N-methylpyrrolidinone, N, N '-Dimethylimidazolidinone, N, N-dimethylacetamide, cyclic urea, preferably 1,3-dimethyl-2-imidazolidinone or 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H ) -Pyrimidinone, glymes, preferably tetraglyme, sulfolane, such as 2-ethanesulfonyl-propane, 1-ethanesulfonyl-2-methyl-propane or 2- (propane-2-sulfonyl) -butane, preferably asymmetrically Substituted sulfones, 3-methyl sulfolane, dimethyl sulfo Such as xoxides, trimethyl phosphates and methoxy substituted nitriles have boiling points higher than 160 ° C, more preferably higher than 190 ° C. Other useful solvents are acetonitrile, benzonitrile and / or valeronitrile.

  If a solvent is present in the electrolyte formulation, it may further include a polymer as a gelling agent, where the polymer is polyvinylidene fluoride, polyvinylidene-hexafluoropropylene, polyvinylidene-hexafluoropropylene- They are chlorotrifluoroethylene copolymer, Nafion, polyylene oxide, polymethyl methacrylate, polyacrylonitrile, polypropylene, polystyrene, polybutadiene, polyethylene glycol, polyvinyl pyrrolidone, polyaniline, polypyrrole, and polythiophene. The purpose of adding these polymers to the electrolyte formulation is to make the liquid electrolyte a quasi-solid or solid electrolyte, thus improving the solvent residue, especially over time.

The electrolyte formulation of the present invention may further comprise a metal oxide such as, for example, SiO ₂ , TiO ₂ , Al ₂ O ₃ , MgO or ZnO, which also increases solidity and hence solvent residue. Can do.

The invention therefore further relates to the use of the electrolyte formulations described in detail above in dye-sensitized solar cells.
The invention therefore further relates to a dye-sensitized solar cell comprising at least one compound of the formula I as described or preferably described herein.

  In one preferred embodiment of the invention, at least one compound of formula I is contained in the electrolyte solution, or in other words, at least one compound of formula I is part of the electrolyte formulation. The dye-sensitized solar cell described above.

  In dye-sensitized solar cells, the dye is used to convert sunlight into electrical energy. As long as the LUMO energy state is slightly above the conduction band edge of the photoelectrode to be sensitized, there is no limit on the choice of dye itself. Examples of dyes are disclosed in EP 0 986 079 A2, EP 1 180 774 A2 or EP 1 507 307 A1.

Preferred dyes are MK-1, MK-2 or MK-3 (its structure is described in FIG. 1 of N. Koumura et al, J. Am. Chem. Soc. Vol 128, no. 44, 2006, 14256-14257. )
D102 (CAS number 652145-28-3), D-149 (CAS number 786643-20-7), D205 (CAS number 936336-21-9), D358 (CAS number 1207638-53-6) T. Bessho et al , Angew. Chem. Int. Ed. Vol 49, 37, 6646-6649, 2010, YD-2, Y123 (CAS No. 1314659-12-1), bipyridine-ruthenium dyes such as N3 (CAS No. 141460-). 19-7), N719 (CAS number 207347-46-4), Z907 (CAS number 502693-09-6), C101 (CAS number 1048964-93-7), C106 (CAS number 11523310-69-4), K19 (CAS number 847665-45-6), SK-1 (CAS number 906061-30-1) or Terpyridine-ruthenium dyes, such as organic dyes such as N749 (CAS number 359415-47-7).

Particularly preferred dyes are Z907 or Z907Na or D205, both of which are amphiphilic ruthenium sensitizers. The dye Z907 means NaRu (2,2′-bipyridine-4-carboxylic acid 4′-carboxylate) (4,4′-dinonyl-2,2′-bipyridine) (NCS) ₂ .

The structure of D205 is
It is.
A very particularly preferred dye is Z907 or Z907Na.

  In a preferred embodiment, the dye is co-adsorbed with phosphinic acid. A preferred example of phosphinic acid is bis (3,3-dimethyl-butyl) -phosphonic acid (DINHOP) described in M. Wang et al, Dalton Trans., 2009, 10015-10020.

  For example, a dye-sensitized solar cell contains a photoelectrode, a counter electrode, and an electrolyte formulation or charge transport metal between the photoelectrode and the counter electrode, where the sensitizing dye faces the counter electrode. Absorbed on the surface of the photoelectrode on the side.

According to a preferred embodiment of the device according to the invention, it comprises a semiconductor, the electrolyte formulation described above and a counter electrode.
According to a preferred embodiment of the present invention, the semiconductor comprises Si, TiO ₂ , SnO ₂ , Fe ₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , CdS, ZnS, PbS, Bi ₂ S ₃ , CdSe, GaP, InP. , GaAs, CdTe, CuInS ₂ and / or based on a metal selected from the group of CuInSe ₂ . Preferably, the semiconductor has a mesoporous surface, thus increasing the surface optionally coated with the dye and in contact with the electrolyte. Preferably, the semiconductor is present on a glass support or plastic or metal foil. Preferably the support is conductive.

  The device of the present invention preferably includes a counter electrode. For example, glassy fluorine-doped tin oxide or tin-doped indium oxide (FTO glass or ITO glass, respectively) coated with Pt, preferably carbon, polyaniline or poly (3,4-ethylenedioxythiophene), which is a conductive allotrope (PEDOT). In addition to glass, metal substrates such as stainless steel or titanium sheets can be possible substrates.

  The device of the present invention can be produced as a corresponding device of the prior art by simply replacing the electrolyte with the electrolyte formulation of the present invention. For example, in the case of dye-sensitized solar cells, device assemblies are described in numerous patent literatures such as WO 91/16719 (eg 34 and 35) as well as scientific literature such as Barbe, CJ, Arendse, F., Comte. , P., Jirousek, M., Lenzmann, F., Shklover, V., Graetzel, MJ Am. Ceram. Soc. 1997, 80, 3157; and Wang, P., Zakeeruddin, SM, Comte, P., Charvet , R., Humphry-Baker, R., Graetzel, MJ Phys. Chem. B 2003, 107, 14336.

  Preferably, the sensitized semiconductor material serves as a photoanode. Preferably, the counter electrode is a cathode.

  The present invention provides a method of manufacturing a photovoltaic cell comprising the steps of contacting the electrolyte formulation of the present invention with a surface of a semiconductor and optionally contacting the surface with a sensitizer. Preferably, the semiconductor is selected from the materials provided above, and the sensitizer is preferably selected from the quantum dots and / or dyes disclosed above, particularly preferably from the dyes.

  Preferably, the electrolyte formulation creates a vacuum in the internal lumen of the cell through the holes in the counter electrode, into a device that is purely purified on the semiconductor, or otherwise already includes a counter electrode. And may be applied by adding electrolyte formulations disclosed in the references of Wang et al., J. Phys. Chem. B 2003, 107, 14336.

  The compounds of formula I described above are commercially available or may be synthesized by methods already known.

  In order to obtain a large group of functional materials for various applications, it has been widely developed to replace the N atom of a heteroaromatic compound with a halogenated material to form a carbon-nitrogen bond. . These heteroaromatic compounds are used as one of the most important primary materials for drug discovery and organic electronics development (eg organic photovoltaics, organic light emitting diodes, organic semiconductor devices) .

  In general, the substitution is for strong bases (eg KH, NaH, LiOH, KOH, NaOH), sometimes phase transfer catalysts (eg tetraalkylammonium salts, crown ethers), organic-aqueous two-phase reactions, electrophile reactions. Requires a combination of an excess of substrate (J. Org. Chem., 1954, 19, 1428; J. Am. Chem), a reactive leaving group (eg iodine or bromine), high reaction temperature and long reaction time Soc., 1984, 106, 6379; Tetrahedron Lett., 1979, 20, 4709-4712; Heterocycles, 1984, 38, 4, 793-802; Tetrahedron, 2004, 60, 5807-5825; Tetrahedron Lett., 2006, 47, 1575-1579; Adv. Mater., 2007, 19, 1133-1137; Polyhedron, 2008, 27, 87-94; J. Am. Chem. Soc., 2008, 130, 12590-12591).

However, under such strong basic conditions at elevated temperatures, undesired reaction course (s), such as nitrogen quaternization, nucleophilic carbon-carbon bond formation can also be observed, for example, in Eq. 2:
In the case of alkylation of benzimidazole as represented in the diagram proceeds simultaneously:

  In addition, in a purification procedure, a difficult extraction (sticky or bulky) salt or polymerized by-product prevents a smooth extraction, separation or filtration process.

In order to solve the problems mentioned above for the synthesis of the compounds of formula I described above for use in dye-sensitized solar cells, the reaction mixture is irradiated with microwaves for a short time ( Apply uniform heat within 20 minutes). The reaction mixture consists of equal equivalents of alkyl halide to the number of substituted nitrogens in the starting material, solvent and base. Bases such as K ₂ CO ₃ particles replace alkali metal hydrides and alkali metal hydroxides with easy handling and safety.

After a short reaction with microwave radiation, only three (3) steps of the purification operation are performed to easily obtain the desired product:
Step 1) The precipitated base and salt in the reaction mixture are filtered off.
Step 2) Evaporate the solvent from the filtered solution under reduced pressure.
Step 3) The substituted product is purified by column chromatography, distillation or recrystallization.

  According to this improved method of N-alkylation and N-alkoxyalkylation, N-substituted heteroaromatic compounds of formula I are prepared in high yield.

Halogenated compounds shall be used as alkylating reagents such as iodide, bromide or chloride.
Solvents such as aprotic, highly polar, medium high boiling organic media such as DMF (N, N-dimethylformamide), DMSO (dimethyl sulfoxide), DMI (1,3-dimethyl-2-imidazolidinone), DBU ( Diazabicycloundecene), preferably DMF, shall be used.

  The typical molar concentration of the microwave reaction is in the range of 0.01-1 mol (mol / L), preferably 0.05-1 mol, more preferably 0.1-0.5 mol in the solvent. is there.

  Inorganic or organic bases, such as inorganic carbonates such as ammonium carbonate, lithium carbonate, potassium carbonate, sodium carbonate, calcium carbonate, barium carbonate, magnesium carbonate, cesium carbonate, silver carbonate or copper carbonate, assisted by the microwave described It shall be used within.

  Typical amounts of base are in the range of 1.1 to 3 equivalents, preferably 1.5 to 3 moles, more preferably 2 to 2.5 equivalents per equivalent of leaving group of the electrophile.

The microwave power is in the range of 200-400 W, preferably 250-300 W.
The reaction temperature is in the range of 100 to 180 ° C, preferably 120 to 140 ° C.
The reaction time is thus in the range from 1 to 30 minutes, preferably from 3 to 20 minutes.

  Without further reference, it is assumed that one skilled in the art can utilize the above description in the broadest scope. The preferred embodiments and examples should therefore merely be considered as descriptive disclosure which is not fully limited in any way.

The synthesized compounds are characterized by NMR spectroscopy or elemental analysis. The NMR spectrum is measured in CDCl ₃ . Frequency used: ¹ H: 399.78 MHz and ¹³ C: 100.52 MHz, external standard: TMS for ¹ H and ¹³ C. ¹ H and ¹³ C NMR spectra were recorded on a JEOL JNM-LA3000 spectrometer. All spectra were recorded at ambient temperature.
Melting point experiments were performed on a METTLER TOLEDO FP90 Central Processor and FP81HT MBC Cell.

Example 1:
Synthesis of N-alkoxyalkylimidazoles:
Add 2.0-3.0 equivalents of base to the imidazole solution and mix with them with vigorous stirring. Next, a solution of 1 equivalent of alkoxyalkyl halide dissolved in solvent is added dropwise and the mixture is irradiated for 3-20 minutes in a microwave oven placed under a hood operating at 200-400 W power. The base solid in the reaction mixture is filtered off after cooling to room temperature and then the solvent is evaporated under reduced pressure. The concentrated residue is purified by distillation or recrystallization after silica gel short column chromatography.

This general procedure applies to N-alkylation of other azoles such as imidazole or benzimidazole.
The following compounds are synthesized according to the process described above.
1- (2-methoxyethyl) -1H-imidazole in 92% yield.

1- (2-Ethoxyethyl) -1H-imidazole in 76% yield.

Example A:
The following electrolyte formulations are synthesized to illustrate the application in dye-sensitized solar cells of the electrolyte formulation of the present invention comprising emim TCB.
Use the following electrolyte formulation:
I ₂ 2.5%, mmimI 43.4%, guaSCN 0.7%, emimTCB 50.4%, 3% in additive w / w described in detail below.

  The electrolyte formulation is prepared by mixing 1,3-dimethylimidazolium iodide (mmimI), 1-methyl-3-ethylimidazolium tetracyanoborate (emimTCB), iodine and guanidinium thiocyanate. It may be necessary to apply heat up to 60 ° C. to make the electrolyte formulation homogeneous.

Compound mmimI, emimI, _{I 2} and emimTCB are either commercially available or known in the literature, for example Bonhote, P et al. Inorg. Chem. 1996, 35, organic salts and 1168-1178 or tetracyanoborate anion For example, the synthesis may be based on WO 2004/072089.

The following additives are used in the electrolyte formulations described above:
Electrolyte 1 1- (2-Ethoxyethyl) -1H-imidazole electrolyte 2 1- (2-methoxyethyl) -1H-imidazole electrolyte 3 1- (methoxymethyl) -1H-imidazole electrolyte 4 1- (ethoxymethyl) -1H -Imidazole

In comparison to the following: electrolyte 5 imidazole electrolyte 6 1-methyl-1H-imidazole electrolyte 7 1- (n-butyl) -1H-imidazole.

  Dye-sensitized solar cells are manufactured as disclosed in US 5,728,487 or WO 2007/093961:

A double layer, mesoporous TiO ₂ electrode is disclosed in Wang P. et al., J. Phys. Chem. B 2003, 107, 14336, in particular page 14337, in order to obtain a photoanode consisting of a double layer structure. Manufactured as follows. To produce the transparent nanoporous TiO ₂ electrodes, a screen printing paste containing nanoparticles of TiO ₂ anatase phase having a diameter of terpineol solvent and 20 to 30 nm, by using a hand printer in 5mm × 5mm square The shape was deposited on a conductive substrate. The paste was dried at 120 celsius for 10 minutes. Then another screen printing paste containing TiO ₂ with a diameter of 400 nm was deposited on top of the nanohard layer to produce an opaque phase.

The bilayer membrane was then sintered at 500 Celsius for 1 hour, resulting in a lower transparent layer (7 microns thick) and a top opaque phase (4 microns thick). After sintering, the electrode was immersed in a 40 mM aqueous solution of TiCl ₄ (Merck) for 30 minutes at 70 Celsius and then rinsed sufficiently quickly with pure water. The electrode thus treated with TiCl ₄ was dried for 30 minutes at 500 Celsius just prior to dye sensitization. The electrodes were soaked in acetonitrile (Merck HPLC grade) and tert-butyl alcohol (Merck), v: v = 1: 1 0.3 mM Z907 dye solution for 60 hours at 19 degrees Celsius. The counter electrode was made by pyrolysis as disclosed in the above reference. A drop of 5 mM solution of platinic acid (Merck) was dropped at 8 μl / cm 2 and dried on a conductive substrate. A dye-sensitized solar cell was assembled using a 30 micron thick Bynel (DuPont, USA) hot melt film and encapsulated by heat. The interior space was filled with the respective electrolyte formulation described herein to produce the corresponding device.

The dye Z907 is an amphiphilic ruthenium sensitizer Ru (2,2′-bipyridine 4,4′-dicarboxylic acid) (4,4′-dinonyl-2,2′-bipyridine) (NCS) ₂ or [Ru (H2dcbpy) (dnbpy) (NCS) ₂ ].

In order to obtain accurate light intensity, Air Mass 1.5 Global (AM1.5G) simulated sunlight is converted into Seigo Ito et al. “Calibration of solar simulator for evaluation of dye-sensitized solar cells” Solar Energy Materials & Solar Cells 82 ( 2004) 421 spectrally calibrated.
Measurement of the photocurrent-voltage curve is performed on a device placed on a black plate cooled to 25 ° C. under 1 Sun illumination. A 4 mm × 4 mm optical mask is placed on top of the manufactured device to define the light projection area.

  The energy conversion efficiency is generally the ratio between the effective output of the energy conversion device and the input of light illumination, and is determined by using an adjustable resistive load that optimizes the power output in the energy term.

The photovoltaic parameters thus obtained are summarized in Table 1:

J _SC = short circuit current V _OC = open circuit voltage FF = fill factor η = power conversion efficiency

  Within these measurements, alkoxyalkylimidazoles give higher efficiency than the additives N-butylimidazole, N-methylimidazole or imidazole.

Example B:
The following electrolyte formulation is synthesized to illustrate the application in a dye-sensitized solar cell of the electrolyte formulation of the present invention comprising 1-butyl-1-methylimidazolium monomethylcyanoborate.
A dye-sensitized solar cell was fabricated according to Example A and measurements were made according to Example A.

  The electrolyte formulation is 1,3-dimethylimidazolium iodide (mmimI), iodine, the additives listed below, 1-butyl-1-methylimidazolium monomethylcyanoborate and one of guanidinium thiocyanate (guaSCN) Alternatively, it is prepared by mixing in two or more of the weight percentages listed below.

8% by weight of electrolyte
I ₂ 1.3
mmim I 35
guaSCN 0.7
1- (2-Ethoxyethyl) -1H-imidazole 3.0
bmim monomethylcyanoborate 60
Total 100

Electrolyte 9
I ₂ 1.3
mmim I 35
guaSCN 0.7
1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole
3.0
bmim monomethylcyanoborate 60
Total 100

Electrolyte 10
I ₂ 1.3
mmim I 35
guaSCN 0.7
1- (2′-thioethyl) ethyl-imidazole 3.0
bmim monomethylcyanoborate 60
Total 100

The photovoltaic parameters thus obtained are summarized in Table 2:

J _SC = short circuit current V _OC = open circuit voltage FF = fill factor η = power conversion efficiency

Example C:
The following electrolyte formulation was synthesized to produce a dye-sensitized solar for the electrolyte formulation of the present invention having an N-butylbenzimidazole containing 1-ethyl-1-methylimidazolium monohydridotricyanoborate. Illustrates application in batteries.

A dye-sensitized solar cell was fabricated according to Example A and measurements were made according to Example A.
Dye-sensitized solar cells are fabricated and measured using Z907 as disclosed in Example A, and similarly using dye C106 / DINHOP, and using dye SK-1.

  For dye C106, the electrode, 0.3 mM for dye C106 and 0.075 mM for DINHOP dye solution (solvent mixture acetonitrile (Merck HPLC grade) and tert-butyl alcohol (Merck), v: v = 1 : 1) was immersed at 6 degrees Celsius for 64 hours.

For dye SK-1, an electrode was prepared according to Example A.
The electrolyte formulation is prepared by mixing the components listed below in weight percent.

Electrolyte 11 * wt%
I ₂ 1.45
mmim I 35.54
guaSCN 0.68
emim monohydridotricyanoborate 59.22
NBB 3.11
Total 100

12% by weight of electrolyte
I ₂ 1.47
mmim I 35.85
guaSCN 0.68
1- (2-Methoxyethyl) -1H-imidazole 2.25
emim monohydridotricyanoborate 59.75
Total 100

Electrolyte 13
I ₂ 1.47
mmim I 35.94
guaSCN 0.69
1-methoxymethyl-1H-imidazole 2.0
emim monohydridotricyanoborate 59.9
Total 100

Electrolyte 14
I ₂ 1.44
mmim I 35.27
guaSCN 0.67
1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole
3.82
emim monohydridotricyanoborate 58.79
Total 100

Table 3 summarizes the results of the measurements of the electrolyte formulations 11-14 cited above:

Within these measurements, alkoxyalkylimidazole has an equal efficiency than the additive N-butylbenzimidazole for dye-sensitized solar cells containing Z907.
As can be shown, the additive 1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole gives equal or higher efficiency compared to NBB.

Example D:
The following electrolyte formulations are synthesized to illustrate the application in dye-sensitized solar cells of the electrolyte formulation of the present invention comprising emim TCB.
The addition concentration is fixed at 0.25 M for each electrolyte 15-20 in addition to the base mixture of the composition:
I ₂ 2.5%, mmimI 51.5%, guaSCN 1.0%, emimTCB 45%.

  The electrolyte formulation is prepared by mixing 1,3-dimethylimidazolium iodide (mmimI), 1-methyl-3-ethylimidazolium tetracyanoborate (emimTCB), iodine and guanidinium thiocyanate. It may be necessary to apply heat up to 60 ° C. to make the electrolyte formulation homogeneous.

Compound mmimI, emimI, _{I 2} and emimTCB are either commercially available or known in the literature, for example Bonhote, P et al. Inorg. Chem. 1996, 35, organic salts and 1168-1178 or tetracyanoborate anion For example, the synthesis may be based on WO 2004/072089.

The following additives are used in the electrolyte formulations described above:
Electrolyte 15 No Additive-Basic Mixture Electrolyte 16 NBB
Electrolyte 17 1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole electrolyte 18 1- (3,3,4,4,4-pentafluorobutyl) -1,2,4-triazole Electrolyte 19 1- (3,3,4,4,4-pentafluorobutyl) -1,2,3-triazole electrolyte 20 N- (3,3,4,4,4-pentafluorobutyl) -benzimidazole.

A dye-sensitized solar cell was fabricated according to Example A and measurements were made according to Example A, but dye C106 is used instead of Z907.
Table 4 summarizes the results of the measurements of the electrolyte formulations 15-20 cited above:

  As can be seen, the additives 1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole and 1- (3,3,4,4,4-pentafluorobutyl) -1 1,2,3-triazole provides higher efficiency compared to NBB.

Claims (14)

In an electrolyte formulation for a dye-sensitized solar cell comprising a redox active species,
Formula I
Where
R ^a , R ^b , R ^c , R ^d and R ^e are independently of each other,
H, F, Cl or linear or branched alkyl having 1 to 20 C atoms, optionally partially or fully fluorinated or chlorinated,
n is 1, 2, 3 or 4;
m is 1, 2, 3 or 4.
Use as additive pressurizing agent THAT least one compound represented. The use according to claim 1, wherein R ^a , R ^b , R ^c , R ^d and R ^{e in} at least one compound of formula I are H or F, independently of one another. The use according to claim 1 or 2, wherein R ^a , R ^b , R ^c , R ^d and R ^{e in} at least one compound of formula I are H. An electrolyte formulation for a dye-sensitized solar cell comprising at least one compound of formula I according to any one of claims 1 to 3 together with a redox active species. Redox active species, a redox pair of iodine and at least one iodide salt, electrolyte formulation of claim 4.   6. Electrolyte formulation according to claim 5, comprising at least one compound of formula I in a concentration of 0.01 to 30% by weight.   The electrolyte formulation according to any one of claims 4 to 6, comprising at least one compound having a tetracyanoborate anion, a dicyanodifluoroborate anion and / or a fluorotricyanoborate anion.   The electrolyte formulation according to any one of claims 4 to 7, comprising at least one salt having an iodide or thiocyanate anion, the cation of which is an inorganic cation, a guanidinium cation or a protonated amine.   9. The electrolyte formulation of claim 8, comprising at least one salt having an iodide or thiocyanate anion, the cation of which is a protonated amine. A dye-sensitized solar cell comprising a dye-sensitized electrode and comprising an electrolyte formulation comprising at least one compound of formula I according to any one of claims 1 to 3 and a redox active species . 1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole or 1- (3,3,4,4) in an electrolyte formulation for dye-sensitized solar cells containing redox active species , 4-pentafluoro-butyl) -1,2,3 use as additive pressurizing agent triazole. Redox at least 1- (3,3,4,4,4-pentafluorobutyl) -1H-imidazole or 1- (3,3,4,4,4-pentafluorobutyl) -1,2,3-triazole An electrolyte formulation for a dye-sensitized solar cell , which is contained together with an active species. Including redox active species, in the electrolyte formulation for the dye-sensitized solar cell, 1- (2'-thioethyl) used as additive pressurizing agent ethylimidazole. An electrolyte formulation for a dye-sensitized solar cell , comprising at least 1- (2′-thioethyl) ethylimidazole together with a redox active species.